Field of the Invention
The present invention relates to a device for performing at least one of detection and emission of electromagnetic waves, and more particularly, to an electromagnetic wave sensor or emitter operating with an electromagnetic wave having an arbitrary frequency band in the frequency range from millimeter waves to terahertz (THz) (30 GHz to 30 THz) (hereinafter also referred to as “terahertz wave”). In the following, the electromagnetic wave sensor and/or emitter is represented by a sensor in some cases.
Description of the Related Art
When terahertz waves are used, imaging of a test object can be realized at a resolution of 1 millimeter or less. In addition, many molecules are sensitive to a specific frequency component in the terahertz range, and hence terahertz waves can be used for the spectroscopic analysis of materials. With this feature of terahertz waves, it is possible to build a system operating in the terahertz range that carries out both imaging and spectroscopic analysis of a test object. For example, an image showing what kind of compound is present at what position of the test object can be formed. Many applications are expected from this feature in the medical field, security field, and manufacturing field.
U.S. Pat. No. 8,344,950 reports on a module comprising a dual-loop and multi-frequency antenna. This module includes a radiating element in which two loops are electrically connected to the same shorting unit and to the same feeding unit, the smaller of the two loops being included into the larger one. The two loops are therefore electrically connected together. This design allows for the simultaneous usage of two frequency bands (2.4 GHz and 5 GHz) for a wireless LAN (local area network) access-point. Thanks to this design using a dual-loop, the antenna of the system can be made smaller than previous dual band antennas and therefore more appealing aesthetically. In order to have a high efficiency, the radiation impedance of the dual-loop antenna and the impedance of the feeding unit must be matched to each other (conjugate matching).